Double-gap spark plug

ABSTRACT

A spark plug having two spark gaps connected in series, the first gap being formed between the main, positive electrode extending lengthwise through the plug and a first electrode finger attached to a conductor sleeve embracing the lower end of the porcelain insulating stem of the plug. The second spark gap is defined between the conductor sleeve and a second electrode finger attached to the conductive base portion of the plug which is secured in threaded engagement with an engine block.

UnitedStat'e's Patent inventor Gustav P. Nylen 5868 Picker St., Arlington, Calif. 92503 Appl. No. 791,446 Filed Jan. 15, 1969 Patented May 4, 1971 624,935 7/1927 France .11..

Primary Examiner-Robert Segal FOREIGN PATENTS Attorney-Williamson, Palmatier and'Bains ABSTRACT: A spark plug having two spark gaps connected in series, the first gap being formed between the main, positive electrode extending lengthwise through the plug and a first electrode finger attached to a conductor sleeve embracing the lower end of the porcelain insulating stem of the plug. The second spark gap is defined between the conductor sleeve and a second electrode finger attached to the conductive base portion of the plug which is secured in threaded engagement with an engine block.

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wmupwww A TTOR/VEYS DOUBLE-GAP SPARK PLUG BRIEF SUMMARY OF THE INVENTION The improved spark plug of this invention is particularly characterized by an arrangement of two spark gaps connected in a series circuit so as to provide a double spark each time a charge of current is distributed to the plug. The two sparks occurring substantially simultaneously insure the complete combustion of the gaseous fuel mixture in a combustion chamber.

I have been able to realize my objective of a multiple gap spark plug in a particularly simple and inexpensive manner by using a conductive sleeve on the lower end of the insulating stern portion of the plug in a unique structural embodiment wherein the sleeve serves to support an electrode finger disposed in spark gap relation to the positive, main electrode and also functions to conduct an electrical impulse jumping across the first spark gap to a second spark gap between the sleeve and a ground electrode depending from the conductive base of the spark plug.

A particularly significant feature of my improved doublegap spark plug resides in the provision of an insulating air space between the aforesaid conductor sleeve and the conductive base of the plug to insure that current flows through the plug base by way of the second spark gap.

These and other objects and advantages of my invention will become readily apparent as the following description is read in conjunction with the accompanying drawings wherein like reference numerals have been used to designate like elements throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation view of the double-gap spark plug of this invention installed in an engine block;

FIG. 2 is a bottom view of the plug of FIG. I on a larger I scale;

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the embodiment of my improved spark plug shown in FIGS. 1-3, an elongated insulating body I encloses a first, positive electrode rod 2 extending longitudinally therethrough. Insulating body I is preferably molded from porcelain, but other insulating materials may be employed. Electrode 2 tenninates at its upper end at a metallic coupling portion 4 adapted to be connected to the female fitting of a conductor lead in the conventional manner. Embracing the lower end of porcelain insulator 1 is a connector member 6 having external threads 7 at one end thereof for threaded engagement within aperture 10 of an engine cylinder head 12. Connector member 6 also includes hexagonal head 8 providing wrench flats by means of which fitting member 6 may be rotated into secure engagement with threaded aperture 10. Connector member or fitting 6 seats 4 within recess 14 of cylinder head 12 in tight contact with sealing gasket 15. The parts heretofore described are standard and well-known components of any spark plug. 7

As a unique feature of my improved spark plug I mount an electrically conductive sleeve 16 on the lower end of insulating body I at the location shown in FIGS. 1 and 3. Sleeve 16 is preferably formed from metal, and is held firmly in place on insulating body 1 by apertures or perforations 17 which tightly engage projecting portions 18 of porcelain body 1. Conductor sleeve 16 is preferably molded in place on the lower end of insulating body I by allowing the porcelain material to flow into apertures 17 when porcelain body I is being molded. A second electrode in the form of finger 20 is attached to sleeve 16 with its free end 21 disposed in closely spaced, sparkgap relation to the bottom end of positive electrode 2 in the manner shown in FIGS. 1 and 3. End 21 of electrode finger 20 lies directly under main electrode 2, as appears most clearly in FIG. 2. In order to provide a second spark gap, I provide a third electrode in the form of a finger or prong 22 which extends between threaded end 7 of connector member 6 and conductive sleeve 16 in conductive relation thereto. Electrode finger 22 could of course be connected to either sleeve 16 or the bottom end of connector member 6. Preferably, finger 22 is connected to threaded end 7 of connector member 6 and depends downwardly therefrom to a terminal point which is spaced spark-gap distance from conductive sleeve 16. The spacial relationship between third electrode 22 and conductive sleeve 16, and the second spark gap defined therebetween, clearly appears in FIGS. 2 and 3.

Referring now to FIG. 3, it will be seen that lower, threaded end 7 of connector fitting 6 is tubular in form and is spaced radially outwardly from the lower end of porcelain body 1, thereby defining an annular insulating air space 24 therebetween. By thus spacing conductive end portion 7 of connector fitting 6 from the lower end of porcelain body 1 and conductive sleeve 16, I am able to insure that current flows from sleeve 16 to conductive end portion 7 of member 6 by jumping to electrode 22. It will readily be appreciated that if conductive end 7 of connector member 6 and conductive sleeve 16 were in direct contact or closely confronting each other, current would flow directly therebetween rather than jumping across thespark gap between sleeve 16 and electrode finger 22. Moreover, the particular structural arrangement shown wherein conductive sleeve 16 is mounted on an end portion of porcelain body I projecting longitudinally beyond threaded end 7 of connector fitting 6- permits the establishment of the second spark gap between sleeve 16 and downwardly depending electrode 22 at a point spaced a sufficient distance from end 7 of member 6 that there is little danger of having the electrical impulse travel directly from sleeve 16 to member 6 and thus bypass electrode finger 22.

In operation, current from a supply source will be conducted to positive, main electrode 2 and will jump from the lower end thereof to terminal point 21 of electrode finger 20 to establish a first ignition spark. The electrical impulse will continue to flow in a series circuit from electrode 20, through conductive sleeve I6 and will jump to electrode 22 across the second spark gap, with the circuit then being completed to ground or a negative side through conductive end 7 of connector member 6 and cylinder head 12. Connector fitting 6 would normally be made of metal, and will thus serve to conduct the electrical impulse to cylinder head 12 for grounding. The double spark thus achieved from a single electrical impulse by directing the current through two electrode fingers 20 and 22 connected in series by means of conductive sleeve 16 greatly enhances the ability of my improved spark plug to accomplish the proper ignition and full combustion of the gaseous fuel in the combustion chamber of an engine.

In FIG. 4 I have shown an alternative embodiment of my improved spark plug which is particularly designed for use with engine cylinder heads having a spark plug receiving aperture which is relatively small in diameter. The spark plug openings in some engines are not large enough to permit the threaded end of connector member 6 to be spaced outwardly from the lower end of porcelain body I to provide annular insulating space 24 in the arrangement shown in FIGS. 2 and 3. For such applications, I contemplate using the spark plug structure shown in FIG. 4 wherein the lower, threaded end 26 of connector fitting 6 snugly embraces the lower end of porcelain body I. By eliminating annular space 24, the outside diameter of threaded end 26 of fitting 6 can be made small enough to be received within relatively small, threaded aperture 11 of cylinder head 12. Conductive sleeve 16 is mounted over the lower end of porcelain body 1 utilizing apertures 17 to engage projecting portions 18 of porcelain body .1 in the manner disclosed above with respect to FIGS. 2 and 3. Electrode finger 20 is connected to and supported by conductive sleeve 16 and is disposed in closely spaced relation to the bottom of main, positive electrode 2 to provide a first spark gap in an arrangement substantially the same as that shown in FIGS. 13.

conductive sleeve 16 and the bottomof threaded end portion I 26 of connector 6, sleeve 16 is mounted on porcelain body 1 in longitudinally spaced relation to threaded connector end 26. Sleeve 16 and connector end 26 are thus spaced longitudinally in the manner shown in FIG. 4 to provide an annular airgap 30 therebetween. By this expedient, the direct conduction of electricity from sleeve 16 to threaded end portion 26 of fitting 6 is prevented. Third electrode finger 32 is mounted in the bottom of threaded end portion 26 of fitting 6 in closely spaced, spark-gap relation to the top of conductive sleeve 16.

The necessary second spark gap is thus provided between prong or finger 32 and the top of sleeve 16. In order that there will be a sufficient surface width freely presented at the top of sleeve 16 to be disposed in conductive relation to electrode finger 32, bottom end 28 of porcelain body 1 is made of slightly larger diameter than the inside diameter of threaded end portion 26 of fitting 6. Sleeve 16 serves as a conductor to complete a series circuit between electrodes 20 and 32 in substantially the same manner as described above with respect to FIGS. 13. Current flowing through positive electrode 2 jumps from the lower end thereof to electrode prong or finger 20 across a first spark gap and is then conducted through sleeve 16 across the second spark gap to electrode finger 32. From electrode 32 the circuit is grounded through the conductive threaded end portion 26 of fitting 6 and cylinder head 12.

I claim:

1. A spark plug comprising:

an elongated, insulating body enclosing a first electrode extendinglongitudinally therethrough and beyond the ends of said body;

an electrically conductive connector member embracing said insulating body, said connector member having an externally threaded end for attachment within a threaded aperture of an engine cylinder head, said threaded end being spaced longitudinally between the ends of said insulating body;

an electrically conductive sleeve secured over the outside of said insulating body adjacent said threaded end of said connector member, the said sleeve'and said connector member spaced longitudinally from one another along the insulating body to form an insulating air space therebetween and to avoid longitudinal overlap of said sleeve and connector member; a second electrode electrically connected to said conductive sleeve and extending therefrom in closely spaced spark gap relation with said first electrode;

a third electrode extending from said threaded 'endof said connector member, and terminating at a point between the ends of said insulating body to cooperate with said sleeve to form a second spark gap therebetween; and

said first electrode, said second electrode, said third electrode and said sleeve cooperating to support two distinct discontinuous sparks, a first spark occurring at an end of the insulating body between said first and second electrodes, and the second spark spaced longitudinally along the insulating body from the first spark and remote therefrom.

2. The combination according to claim 1 wherein:

said insulating body has a circular cross section and a central axis therethrough, the axis passing longitudinally through said first electrode;

a cylindrical shoulder is formed on the insulating body adjoining the end thereof which is adjacent said first electrode, the said shoulder extending radially outward from and coaxial with said insulating body;

said third electrode is secured to the connector member extending longitudinally therefrom relative to said axis, the third electrode and said sleeve being at equal distances from the axis of said insulating body and spacedlongitudinall apart to form alon itudinal spark ap; and

said first spark occurring su stantially axialFy'r insulating body and said second spark occurring longitudinally between the sleeve and said third electrode.

lative to the I 

1. A spark plug comprising: an elongated, insulating body enclosing a first electrode extending longitudinally therethrough and beyond the ends of said body; an electrically conductive connector member embracing said insulating body, said connector member having an externally threaded end for attachment within a threaded aperture of an engine cylinder head, said threaded end being spaced longitudinally between the ends of said insulating body; an electrically conductive sleeve secured over the outside of said insulating body adjacent said threaded end of said connector member, the said sleeve and said connector member spaced longitudinally from one another along the insulating body to form an insulating air space therebetween and to avoid longitudinal overlap of said sleeve and connector member; a second electrode electrically connected to said conductive sleeve and extending therefrom in closely spaced spark gap relation with said first electrode; a third electrode extending from said threaded end of said connector member, and terminating at a point between the ends of said insulating body to cooperate with said sleeve to form a second spark gap therebetween; and said first electrode, said second electrode, sAid third electrode and said sleeve cooperating to support two distinct discontinuous sparks, a first spark occurring at an end of the insulating body between said first and second electrodes, and the second spark spaced longitudinally along the insulating body from the first spark and remote therefrom.
 2. The combination according to claim 1 wherein: said insulating body has a circular cross section and a central axis therethrough, the axis passing longitudinally through said first electrode; a cylindrical shoulder is formed on the insulating body adjoining the end thereof which is adjacent said first electrode, the said shoulder extending radially outward from and coaxial with said insulating body; said third electrode is secured to the connector member extending longitudinally therefrom relative to said axis, the third electrode and said sleeve being at equal distances from the axis of said insulating body and spaced longitudinally apart to form a longitudinal spark gap; and said first spark occurring substantially axially relative to the insulating body and said second spark occurring longitudinally between the sleeve and said third electrode. 